Michael i



(NOMOdeL) M. I. PUPIN.

TRANSFORMER EOR TELBGRAPHIG, TELBPHONIO, OR OTHER ELEOTRIOAL SYSTEMS.

NO. 519,347. 113 1, Patented May 8, 1894.

W'izzasex- UNITED STATES PATENT OFFICE.

MICHAEL I. PUPIN, OF NEW YORK, N. Y.

TRANSFORMER FOR TELEGRAPI- IIC, TELEPHONIC, OR OTHER ELECTRICAL SYSTEMS.

SPECIFICATION forming part of Letters Patent No. 519,347, dated May 8,1894.

Application filed February 10, 1894:. Serial No. 499 7l6- (No model.) I

conductor having in circuit telephone or telegraph instruments, or both.When the secondary coil of an induction transformer consists of a largenumber of turns of wire, it then possesses defects which materiallyimpair its efficiency. First, its electrostatic capacity checks theseparated electrifications in their exit from the coil. Second, thenormally large self induction gives the secondary coil too large a timeconstant and renders it very inefficient when acted upon by electromotive forces of high frequencies. This evil is especially serious incase of induction transformers which are used in connection withtelephone transmitters, because the self induction of the secondarycoils of such transformers tends to weaken the upper harmonics and so todistort the voice. If, however, the secondary coil of such a transformerbe divided into anumber of preferably equal parts or sections, and theseplaced in series and in inductive relation by disposing condensersbetween the successive sections, then I have discovered that both thecapacity effect of the coil can be reduced to any desirable limit, andthe time constant may also be made as small as may be Wished. If such atransformer be combined with a line conductor also divided intosections, arranged in inductive relation and in series, or in otherwords, provided with condensers between the sections, and if both theline and the transformer coil be properly tuned then the rapidity oftransmission may be exceedingly great, the number of messages which maybe transmitted over such a line is independent of electrical conditions,simultaneous telephony and telegraphy is practicable, and a telephoniccurrent will control a recording telegraphic receiver.

Referring to the accompanying drawings: Figure 1 is a partiallongitudinal section showing the construction of my transformer. Fig. 2shows said transformer connected with a telephone line. Fig. 3, showsthe arrangement of the same line for both telegraphic and telephonicpurposes.

Similar letters and figures of reference in dicate like parts.

In Fig. 1, A is the core of the transformer, preferably of fine ironwire, which is surrounded by the primary coil B. Inclosing the primarycoil B is a spool 0, upon which is wound the secondary coil D. Saidsecondary coil is divided into a number of preferably equal parts orsections as a a, b b, c c, 850. Between these parts are interposed theequal or nearly equal condensers, 1, 2, 3, 4, so that the said sectionsand the said condensers are connected in series. The size of the variouscoils and condensers determines the time constant of the whole secondarycoil D. It is not, of course, essential to divide the secondary coilinto equal parts, or to insert equal condensers in order to shorten thetime constant, for the latter will always be between the shortest andlongest time constantof the various parts. So also the various sectionsof the coil can be connected partly in series and partly in parallel, orany like adjustment be made.

I will now describe the arrangement of my said transformer incombination with a telephone line. It is to be nnderstoodthat the lineconductor here illustrated is not specifically claimed in thisapplication, because it forms the subject matter of another applicationforLetters Patent, Serial No. 493,651, already filed by me December 14,1893, and now pending. Referring to Fig. 2 in circuit with the primaryB. of the transformer is a telephone transmitterE of any suitableconstruction and a source of electricity F.

The terminals of the secondary D are connected with the line conductorG, which is made up of sections as g 9, between which sections areinterposed the condensers h, h, &c.

H is a telephone receiver in circuit.

The arrangement of the line for telegraphic or combined telephonic andtelegraphic purposes is represented in Fig. 3. The line terminals at w yare connected to the terminals of the secondary coil D as in Fig. 2. AtI is a telegraphic key. At the distant station is arranged a relayconnected with the line. This maybe of any desired form and operateeither to open and close a circuit or to produce variations of currentstrength therein. Thus there may be an electro-magnet J connected toline and operating the diaphragm of a telephone transmitter K in localcircuit with the primary of an induction coil L, the secondary of whichcoil is in circuit with the metal drum m and the marking point it. Overthe drum may be drawn by clockwork 0 or any other suitable means a stripof chemically prepared paper 12 which will be marked wherever thecurrent passes through it as it is carried between the point it and drumon. The paper is of course moved along at a uniform rate of speed. Theimpressed electromotive force in the primary circuit of the transformerat the transmitting end, may be caused by the telephone transmitterE setin operation by the voice or by any sounding apparatus such as an organreed in front of it or by an alternating current dynamo. The inducedcurrent on the secondary is interrupted in the usual way to send Morsesignals for example by the key I. It is advisable that the periodicityof the impressed electromotive force be as nearly equal to theperiodicity of the circuit as practicable. If the secondary of thetransformer is tuned to a high pitch and the line he also tuned to thesame high pitch, then any known means for very rapid telegraphy, such asthe WVheatstone system may be employed, and the number of messages thatcan be transmitted will be limited only by the mechanism of thetransmitting and receiving devices, and not by any electricalconditions. hen an alternating current generator is employed to feed theprimary of such a transformer, then the primary coil also maybe dividedinto a suitable number of parts in the same way as the secondary withcondensers in like manner interposed. This is especially desirable whenthe primary haslargeself-induction. The inetallicreturn shown in Figs. 2and 3 is not essential, as the line can be grounded in the usual way.

Long telephone lines act in consequence of their distributed capacitylike lines of low impedence, that is to say, a comparatively speakinglow electromotive force at the transmitting end can produce a largecurrent at that end, but a very small part of this initial large currentreaches the receiving end of the line. This effect is well known and isattributed to the attenuating effect of theline. Owing to thisattenuating power of the line, it becomes necessary to work withtransmitters which are capable of sustaining a large current in thesecondary core of the trans former, that is to say, the number of turnsin the secondary coil must be kept low. Briefly stated, long distancetelephone lines are worked today on the principle of large current andlow voltage. But in a long distance line of very high impedence but noattenuating power, it is desirable to work with high electromotiveforces and small currents. Hence, the induction transformer of thetransmitter must have a much larger number of turns in the secondary,than the transformer now in use. But on account of the well known factthat high self induction kills upper harmonics, it is evident that alarge number of turns in the secondary cannot be employed unlesssomedevice isintroduced whichwill diminish the tendency of the selfinduction of the coil to weed out the upper harmonics. This isaccomplished by dividing the secondary coil into sections andinterposing condensers as hereinbefore described, so that thus I may usevery high electromotive force without weakening of the upper harmonics.It will be seen therefore that by-this invention I may operate a longdistance telephone line on the opposite principle from that nowfollowed; that is instead of using low electromotive forces and largecurrents, I may employ high electromotive forces and small currents.

I claim- 1. A transformer having one of its coils divided into sections,the said sections being connected in series and in electrostaticinductive relation and each section being tuned to a certainpredetermined periodicity.

2. A transformer having its secondary coil divided into sections, andcondensers connected in series and interposed between said sections andeach section being tuned to a certain predetermined periodicity.

3. A transformer having its primary coil in circuit with a source ofelectricity anda means of varying the electrical condition of saidcircuit, and its secondary coil connected to a line conductor, the saidsecondary coil and line conductor being each divided into sections, thesaid sections being placed in series and in electrostatic inductiverelation.

4. A transformer having its primary coil in circuit with a source ofelectricity and a means of varying the electrical condition of saidcircuit and its secondary coil connected to a line conductor, the saidsecondary coil and line conductor being each divided into sections thesaid sections being placed in series in electrostatic inductive relationand each tuned to a certain predetermined periodicity.

5. A transformer having its primary coil in circuit with asource ofelectricityand a means of varying the electrical condition of saidcircuit and its secondary coil connected to a line conductor andcondensers, the said secondary coil and line conductor being eachdivided into sections, and connected in series with said condensers: andthe said sections being tuned so that the total periodicity of thesecondary coil and line conductor shall equal or very nearly equal acertain predetermined periodicity.

6. In combination a transformer havingits primary coil in circuit with asource of electricity and a telephone transmitter, and a secondary coildivided into sections disposed in series and in electrostatic relation:a line IIC' conductor also divided into sections disposed in series andin electrostatic inductive relation, and a telephone receiver connectedwith said line conductor. r

7. In combination a transformer having its primary coil in circuit witha source of electricity and a telegraphic transmitter and a secondarycoil divided into sections disposed in series and in electrostaticinductive relation,a line conductor also divided into sections disposedin series and in electrostatic relation, and a telegraphic receiverconnected with said line conductor.

8. In combination, a transformer having its primary coil in electricalcircuit with a telephone, and its secondary coil divided into sectionsdisposed in series and in electrostatic Witnesses:

H. R. MOLLER, E. MnRTIN.

